1. Field of the Invention
The present invention relates to a color filter of a liquid crystal display (LCD) and, more particularly, to a color filter of an LCD that can implement 6 primary colors by adding cyan (C), magenta (M) and yellow (Y) complementary colors to a color reproduction range using the existing red (R), green (G) and blue (B).
2. Discussion of the Related Art
In general, an LCD includes two display panels and a liquid crystal layer, which has dielectric anisotropy, interposed between the two display panels.
In the LCD, an electric field is applied to the liquid crystal layer, and the strength of the electric field is controlled to adjust transmittance of light that passes through the liquid crystal layer to obtain a desired image.
The LCD is a typical device among portable flat panel displays (FPDs), and a thin film transistor (TFT) LCD including TFTs as switching elements is commonly used.
The LCD includes a plurality of sub-pixels including pixel electrodes (not shown) and red, green and blue color filters.
Each sub-pixel is driven by a signal applied via a display signal line to perform a display operation.
Signal lines include gate lines (or scan signal lines) that transfer scan signals and data lines that transfer data signals. Each sub-pixel includes a TFT which is connected with a single gate line and a single data line, through which an image signal transferred to a pixel electrode formed in the sub-pixel is controlled.
In the related art LCD, the red (R), green (G) and blue (B) color filters are arranged in various forms.
For example, in a stripe type color filter arrangement, the same color filters are arranged in units of sub-pixel rows. In a mosaic type color filter arrangement, the red (R), green (G) and blue (B) color filters are sequentially arranged in rows and columns. In a delta type color filter arrangement, sub-pixels are disposed in zigzags in a column direction, and red (R), green (G) and blue (B) color filters are sequentially arranged.
The related art LCD using the delta-type color filter arrangement method will now be described with reference to FIGS. 1 and 2.
FIG. 1 is a plan view showing sub-pixels constituting a single pixel of the related art LCD, and FIG. 2 is a sectional view of the sub-pixels constituting a single pixel of the LCD, taken along line II-II in FIG. 1.
Although not shown, the related art LCD may include a liquid crystal panel that displays a desired image, and a backlight unit that supplies light to the liquid crystal panel.
Here, the liquid crystal panel (not shown) includes a TFT array substrate (not shown) on which TFTs are formed, a color filter substrate (not shown) which is attached to the TFT array substrate and includes red (R), green (G) and blue (B) color filters, and a liquid crystal layer (not shown) filled between the TFT array substrate and the color filter substrate.
A backlight unit of the LCD includes a plurality of lamps to provide light to the liquid crystal panel.
With reference to FIG. 1 and FIG. 2, three sub-pixels including red (R), green (G) and blue (B) color filters 13a, 17a and 21a constituting a single unit pixel 10 are formed on the color filter substrate 11. Here, the color filters 13a, 17a and 21a will be considered to refer to the sub-pixels.
The red (R), green (G) and blue (B) color filters 13a, 17a and 21a are arranged in a column direction.
A black matrix layer (not shown) is formed to block light at boundaries of the red (R), green (G) and blue (B) color filters 13a, 17a and 21a. 
The method for fabricating the color filters of the LCD according to the related art having such array structure will now be described with reference to FIGS. 3a to 3e. 
FIGS. 3a to 3e are sectional views sequentially showing the process of fabricating sub-pixels constituting a single pixel of the related art LCD.
With reference to FIG. 3A, first, a black matrix layer (not shown) is formed on the color filter substrate 11, a glass substrate, for example, with an opaque material in order to prevent light transmission to portions other than the unit pixel area.
Next, one of a color, which is among red, green and blue, resin layer is coated on the color filter substrate 11 including the black matrix layer (not shown). Here, for example, the red color resin layer 13, among the red, green and blue color resin layers, may first be coated.
Then, the red color resin layer 13 is selectively removed through exposing and developing processes using photolithography to form a red color resin layer pattern 13a. In this case, the red color resin layer pattern 13a is used as a red color filter and corresponds to the red sub-pixel.
Subsequently, as shown in FIG. 3b, a green (G) color resin layer 17 is coated on the color filter substrate 11 including the red color resin layer pattern 13a. 
Then, as shown in FIG. 3c, the green color resin layer 17 is selectively removed through exposing and developing processes using photolithography to form the green color resin layer pattern 17a. In this case, the green color resin layer pattern 17a is used as a green color filter and corresponds to the green sub-pixel.
Thereafter, as shown in FIG. 3d, a blue (B) color resin layer 21 is coated on the color filter substrate 11 including the red and green color resin layer patterns 13a and 17a. 
And then, as shown in FIG. 3e, the blue color resin layer 21 is selectively removed through exposing and developing processes using photolithography to form the blue color resin layer pattern 21a. In this case, the blue color resin layer pattern 21a is used as a blue color filter and corresponds to a blue sub-pixel.
The color filters of the related art LCD fabricated as described above and the fabrication method have the following problems.
That is, in the color filters of the related art LCD and its fabrication method, only the three R, G and B colors are used to form the color filters, and as shown in FIG. 4, formation of the color filters with three colors has limited color reproduction characteristics close to the natural colors.
Thus, a method of adding three cyan, magenta and yellow color filters to the three R, G and B color filters has been proposed, which, however, has failed to be employed for mass production because it incurs high fabrication costs for development of additional color inks (cyan, magenta and yellow) and an additional photo process.